1. Field of the Invention
The present invention relates to a method for manufacturing a photoelectric conversion device, and more specifically to micro-lens alignment.
2. Description of the Related Art
Typical examples of photoelectric conversion devices include complementary metal oxide semiconductor (CMOS) image sensors and charge coupled device (CCD) image sensors. Such typical photoelectric conversion devices include micro lenses that collect light incident on photoelectric conversion elements.
Japanese Patent Laid-Open No. 2003-273342 discloses that an isolation region is formed and a photoelectric conversion element is formed using the isolation region as a reference of alignment. Japanese Patent Laid-Open No. 2003-273342 further discloses that a gate layer is formed using the isolation region as a reference of alignment and that each contact plug layer is formed using the gate layer as a reference of alignment. It is also disclosed that a color filter is formed by performing alignment using the gate layer as a reference and that an on-chip lens (micro lens) is formed by performing alignment using the color filter as a reference.
In the method described in Japanese Patent Laid-Open No. 2003-273342, when a micro lens is to be formed, alignment errors that can be caused during previous alignments are accumulated through the formation of the gate layer and the formation of the color filter. As a result, the relative positional relationship between the photoelectric conversion element and the micro lens may be significantly deviated from the design value.
Such deviation may lead to a reduction in the performance of the photoelectric conversion device, such as the occurrence of crosstalk or a reduction in sensitivity as a distance (pixel pitch) between a plurality of photoelectric conversion elements decreases.